// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * lm75.c - Part of lm_sensors, Linux kernel modules for hardware
 *	 monitoring
 * Copyright (c) 1998, 1999  Frodo Looijaard <frodol@dds.nl>
 */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/jiffies.h>
 #include <linux/i2c.h>
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
 #include <linux/err.h>
 #include <linux/of.h>
 #include <linux/regmap.h>
 #include <linux/util_macros.h>
 #include <linux/regulator/consumer.h>
 #include "lm75.h"
 
 /*
  * This driver handles the LM75 and compatible digital temperature sensors.
  */
 
 enum lm75_type {		/* keep sorted in alphabetical order */
     adt75,
     at30ts74,
     ds1775,
     ds75,
     ds7505,
     g751,
     lm75,
     lm75a,
     lm75b,
     max6625,
     max6626,
     max31725,
     mcp980x,
     pct2075,
     stds75,
     stlm75,
     tcn75,
     tmp100,
     tmp101,
     tmp105,
     tmp112,
     tmp175,
     tmp275,
     tmp75,
     tmp75b,
     tmp75c,
     tmp1075,
 };
 
 /**
  * struct lm75_params - lm75 configuration parameters.
  * @set_mask:		Bits to set in configuration register when configuring
  *			the chip.
  * @clr_mask:		Bits to clear in configuration register when configuring
  *			the chip.
  * @default_resolution:	Default number of bits to represent the temperature
  *			value.
  * @resolution_limits:	Limit register resolution. Optional. Should be set if
  *			the resolution of limit registers does not match the
  *			resolution of the temperature register.
  * @resolutions:	List of resolutions associated with sample times.
  *			Optional. Should be set if num_sample_times is larger
  *			than 1, and if the resolution changes with sample times.
  *			If set, number of entries must match num_sample_times.
  * @default_sample_time:Sample time to be set by default.
  * @num_sample_times:	Number of possible sample times to be set. Optional.
  *			Should be set if the number of sample times is larger
  *			than one.
  * @sample_times:	All the possible sample times to be set. Mandatory if
  *			num_sample_times is larger than 1. If set, number of
  *			entries must match num_sample_times.
  */
 
 struct lm75_params {
     u8			set_mask;
     u8			clr_mask;
     u8			default_resolution;
     u8			resolution_limits;
     const u8		*resolutions;
     unsigned int		default_sample_time;
     u8			num_sample_times;
     const unsigned int	*sample_times;
 };
 
 /* Addresses scanned */
 static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
                     0x4d, 0x4e, 0x4f, I2C_CLIENT_END };
 
 /* The LM75 registers */
 #define LM75_REG_TEMP		0x00
 #define LM75_REG_CONF		0x01
 #define LM75_REG_HYST		0x02
 #define LM75_REG_MAX		0x03
 #define PCT2075_REG_IDLE	0x04
 
 /* Each client has this additional data */
 struct lm75_data {
     struct i2c_client		*client;
     struct regmap			*regmap;
     struct regulator		*vs;
     u8				orig_conf;
     u8				current_conf;
     u8				resolution;	/* In bits, 9 to 16 */
     unsigned int			sample_time;	/* In ms */
     enum lm75_type			kind;
     const struct lm75_params	*params;
 };
 
 /*-----------------------------------------------------------------------*/
 
 static const u8 lm75_sample_set_masks[] = { 0 << 5, 1 << 5, 2 << 5, 3 << 5 };
 
 #define LM75_SAMPLE_CLEAR_MASK	(3 << 5)
 
 /* The structure below stores the configuration values of the supported devices.
  * In case of being supported multiple configurations, the default one must
  * always be the first element of the array
  */
 static const struct lm75_params device_params[] = {
     [adt75] = {
         .clr_mask = 1 << 5,	/* not one-shot mode */
         .default_resolution = 12,
         .default_sample_time = MSEC_PER_SEC / 10,
     },
     [at30ts74] = {
         .set_mask = 3 << 5,	/* 12-bit mode*/
         .default_resolution = 12,
         .default_sample_time = 200,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 25, 50, 100, 200 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [ds1775] = {
         .clr_mask = 3 << 5,
         .set_mask = 2 << 5,	/* 11-bit mode */
         .default_resolution = 11,
         .default_sample_time = 500,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 125, 250, 500, 1000 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [ds75] = {
         .clr_mask = 3 << 5,
         .set_mask = 2 << 5,	/* 11-bit mode */
         .default_resolution = 11,
         .default_sample_time = 600,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 150, 300, 600, 1200 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [stds75] = {
         .clr_mask = 3 << 5,
         .set_mask = 2 << 5,	/* 11-bit mode */
         .default_resolution = 11,
         .default_sample_time = 600,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 150, 300, 600, 1200 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [stlm75] = {
         .default_resolution = 9,
         .default_sample_time = MSEC_PER_SEC / 6,
     },
     [ds7505] = {
         .set_mask = 3 << 5,	/* 12-bit mode*/
         .default_resolution = 12,
         .default_sample_time = 200,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 25, 50, 100, 200 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [g751] = {
         .default_resolution = 9,
         .default_sample_time = MSEC_PER_SEC / 10,
     },
     [lm75] = {
         .default_resolution = 9,
         .default_sample_time = MSEC_PER_SEC / 10,
     },
     [lm75a] = {
         .default_resolution = 9,
         .default_sample_time = MSEC_PER_SEC / 10,
     },
     [lm75b] = {
         .default_resolution = 11,
         .default_sample_time = MSEC_PER_SEC / 10,
     },
     [max6625] = {
         .default_resolution = 9,
         .default_sample_time = MSEC_PER_SEC / 7,
     },
     [max6626] = {
         .default_resolution = 12,
         .default_sample_time = MSEC_PER_SEC / 7,
         .resolution_limits = 9,
     },
     [max31725] = {
         .default_resolution = 16,
         .default_sample_time = MSEC_PER_SEC / 20,
     },
     [tcn75] = {
         .default_resolution = 9,
         .default_sample_time = MSEC_PER_SEC / 18,
     },
     [pct2075] = {
         .default_resolution = 11,
         .default_sample_time = MSEC_PER_SEC / 10,
         .num_sample_times = 31,
         .sample_times = (unsigned int []){ 100, 200, 300, 400, 500, 600,
         700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700,
         1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700,
         2800, 2900, 3000, 3100 },
     },
     [mcp980x] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode */
         .default_resolution = 12,
         .resolution_limits = 9,
         .default_sample_time = 240,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 30, 60, 120, 240 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp100] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode */
         .default_resolution = 12,
         .default_sample_time = 320,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 40, 80, 160, 320 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp101] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode */
         .default_resolution = 12,
         .default_sample_time = 320,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 40, 80, 160, 320 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp105] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode*/
         .default_resolution = 12,
         .default_sample_time = 220,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 28, 55, 110, 220 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp112] = {
         .set_mask = 3 << 5,	/* 8 samples / second */
         .clr_mask = 1 << 7,	/* no one-shot mode*/
         .default_resolution = 12,
         .default_sample_time = 125,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 125, 250, 1000, 4000 },
     },
     [tmp175] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode*/
         .default_resolution = 12,
         .default_sample_time = 220,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 28, 55, 110, 220 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp275] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode*/
         .default_resolution = 12,
         .default_sample_time = 220,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 28, 55, 110, 220 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp75] = {
         .set_mask = 3 << 5,	/* 12-bit mode */
         .clr_mask = 1 << 7,	/* not one-shot mode*/
         .default_resolution = 12,
         .default_sample_time = 220,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 28, 55, 110, 220 },
         .resolutions = (u8 []) {9, 10, 11, 12 },
     },
     [tmp75b] = { /* not one-shot mode, Conversion rate 37Hz */
         .clr_mask = 1 << 7 | 3 << 5,
         .default_resolution = 12,
         .default_sample_time = MSEC_PER_SEC / 37,
         .sample_times = (unsigned int []){ MSEC_PER_SEC / 37,
             MSEC_PER_SEC / 18,
             MSEC_PER_SEC / 9, MSEC_PER_SEC / 4 },
         .num_sample_times = 4,
     },
     [tmp75c] = {
         .clr_mask = 1 << 5,	/*not one-shot mode*/
         .default_resolution = 12,
         .default_sample_time = MSEC_PER_SEC / 12,
     },
     [tmp1075] = { /* not one-shot mode, 27.5 ms sample rate */
         .clr_mask = 1 << 5 | 1 << 6 | 1 << 7,
         .default_resolution = 12,
         .default_sample_time = 28,
         .num_sample_times = 4,
         .sample_times = (unsigned int []){ 28, 55, 110, 220 },
     }
 };
 
 static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
 {
     return ((temp >> (16 - resolution)) * 1000) >> (resolution - 8);
 }
 
 static int lm75_write_config(struct lm75_data *data, u8 set_mask,
                  u8 clr_mask)
 {
     u8 value;
 
     clr_mask |= LM75_SHUTDOWN;
     value = data->current_conf & ~clr_mask;
     value |= set_mask;
 
     if (data->current_conf != value) {
         s32 err;
 
         err = i2c_smbus_write_byte_data(data->client, LM75_REG_CONF,
                         value);
         if (err)
             return err;
         data->current_conf = value;
     }
     return 0;
 }
 
 static int lm75_read(struct device *dev, enum hwmon_sensor_types type,
              u32 attr, int channel, long *val)
 {
     struct lm75_data *data = dev_get_drvdata(dev);
     unsigned int regval;
     int err, reg;
 
     switch (type) {
     case hwmon_chip:
         switch (attr) {
         case hwmon_chip_update_interval:
             *val = data->sample_time;
             break;
         default:
             return -EINVAL;
         }
         break;
     case hwmon_temp:
         switch (attr) {
         case hwmon_temp_input:
             reg = LM75_REG_TEMP;
             break;
         case hwmon_temp_max:
             reg = LM75_REG_MAX;
             break;
         case hwmon_temp_max_hyst:
             reg = LM75_REG_HYST;
             break;
         default:
             return -EINVAL;
         }
         err = regmap_read(data->regmap, reg, &regval);
         if (err < 0)
             return err;
 
         *val = lm75_reg_to_mc(regval, data->resolution);
         break;
     default:
         return -EINVAL;
     }
     return 0;
 }
 
 static int lm75_write_temp(struct device *dev, u32 attr, long temp)
 {
     struct lm75_data *data = dev_get_drvdata(dev);
     u8 resolution;
     int reg;
 
     switch (attr) {
     case hwmon_temp_max:
         reg = LM75_REG_MAX;
         break;
     case hwmon_temp_max_hyst:
         reg = LM75_REG_HYST;
         break;
     default:
         return -EINVAL;
     }
 
     /*
      * Resolution of limit registers is assumed to be the same as the
      * temperature input register resolution unless given explicitly.
      */
     if (data->params->resolution_limits)
         resolution = data->params->resolution_limits;
     else
         resolution = data->resolution;
 
     temp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
     temp = DIV_ROUND_CLOSEST(temp  << (resolution - 8),
                  1000) << (16 - resolution);
 
     return regmap_write(data->regmap, reg, (u16)temp);
 }
 
 static int lm75_update_interval(struct device *dev, long val)
 {
     struct lm75_data *data = dev_get_drvdata(dev);
     unsigned int reg;
     u8 index;
     s32 err;
 
     index = find_closest(val, data->params->sample_times,
                  (int)data->params->num_sample_times);
 
     switch (data->kind) {
     default:
         err = lm75_write_config(data, lm75_sample_set_masks[index],
                     LM75_SAMPLE_CLEAR_MASK);
         if (err)
             return err;
 
         data->sample_time = data->params->sample_times[index];
         if (data->params->resolutions)
             data->resolution = data->params->resolutions[index];
         break;
     case tmp112:
         err = regmap_read(data->regmap, LM75_REG_CONF, &reg);
         if (err < 0)
             return err;
         reg &= ~0x00c0;
         reg |= (3 - index) << 6;
         err = regmap_write(data->regmap, LM75_REG_CONF, reg);
         if (err < 0)
             return err;
         data->sample_time = data->params->sample_times[index];
         break;
     case pct2075:
         err = i2c_smbus_write_byte_data(data->client, PCT2075_REG_IDLE,
                         index + 1);
         if (err)
             return err;
         data->sample_time = data->params->sample_times[index];
         break;
     }
     return 0;
 }
 
 static int lm75_write_chip(struct device *dev, u32 attr, long val)
 {
     switch (attr) {
     case hwmon_chip_update_interval:
         return lm75_update_interval(dev, val);
     default:
         return -EINVAL;
     }
     return 0;
 }
 
 static int lm75_write(struct device *dev, enum hwmon_sensor_types type,
               u32 attr, int channel, long val)
 {
     switch (type) {
     case hwmon_chip:
         return lm75_write_chip(dev, attr, val);
     case hwmon_temp:
         return lm75_write_temp(dev, attr, val);
     default:
         return -EINVAL;
     }
     return 0;
 }
 
 static umode_t lm75_is_visible(const void *data, enum hwmon_sensor_types type,
                    u32 attr, int channel)
 {
     const struct lm75_data *config_data = data;
 
     switch (type) {
     case hwmon_chip:
         switch (attr) {
         case hwmon_chip_update_interval:
             if (config_data->params->num_sample_times > 1)
                 return 0644;
             return 0444;
         }
         break;
     case hwmon_temp:
         switch (attr) {
         case hwmon_temp_input:
             return 0444;
         case hwmon_temp_max:
         case hwmon_temp_max_hyst:
             return 0644;
         }
         break;
     default:
         break;
     }
     return 0;
 }
 
 static const struct hwmon_channel_info * const lm75_info[] = {
     HWMON_CHANNEL_INFO(chip,
                HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
     HWMON_CHANNEL_INFO(temp,
                HWMON_T_INPUT | HWMON_T_MAX | HWMON_T_MAX_HYST),
     NULL
 };
 
 static const struct hwmon_ops lm75_hwmon_ops = {
     .is_visible = lm75_is_visible,
     .read = lm75_read,
     .write = lm75_write,
 };
 
 static const struct hwmon_chip_info lm75_chip_info = {
     .ops = &lm75_hwmon_ops,
     .info = lm75_info,
 };
 
 static bool lm75_is_writeable_reg(struct device *dev, unsigned int reg)
 {
     return reg != LM75_REG_TEMP;
 }
 
 static bool lm75_is_volatile_reg(struct device *dev, unsigned int reg)
 {
     return reg == LM75_REG_TEMP || reg == LM75_REG_CONF;
 }
 
 static const struct regmap_config lm75_regmap_config = {
     .reg_bits = 8,
     .val_bits = 16,
     .max_register = PCT2075_REG_IDLE,
     .writeable_reg = lm75_is_writeable_reg,
     .volatile_reg = lm75_is_volatile_reg,
     .val_format_endian = REGMAP_ENDIAN_BIG,
     .cache_type = REGCACHE_MAPLE,
     .use_single_read = true,
     .use_single_write = true,
 };
 
 static void lm75_disable_regulator(void *data)
 {
     struct lm75_data *lm75 = data;
 
     regulator_disable(lm75->vs);
 }
 
 static void lm75_remove(void *data)
 {
     struct lm75_data *lm75 = data;
     struct i2c_client *client = lm75->client;
 
     i2c_smbus_write_byte_data(client, LM75_REG_CONF, lm75->orig_conf);
 }
 
 static const struct i2c_device_id lm75_ids[];
 
 static int lm75_probe(struct i2c_client *client)
 {
     struct device *dev = &client->dev;
     struct device *hwmon_dev;
     struct lm75_data *data;
     int status, err;
     enum lm75_type kind;
 
     if (client->dev.of_node)
         kind = (uintptr_t)of_device_get_match_data(&client->dev);
     else
         kind = i2c_match_id(lm75_ids, client)->driver_data;
 
     if (!i2c_check_functionality(client->adapter,
             I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
         return -EIO;
 
     data = devm_kzalloc(dev, sizeof(struct lm75_data), GFP_KERNEL);
     if (!data)
         return -ENOMEM;
 
     data->client = client;
     data->kind = kind;
 
     data->vs = devm_regulator_get(dev, "vs");
     if (IS_ERR(data->vs))
         return PTR_ERR(data->vs);
 
     data->regmap = devm_regmap_init_i2c(client, &lm75_regmap_config);
     if (IS_ERR(data->regmap))
         return PTR_ERR(data->regmap);
 
     /* Set to LM75 resolution (9 bits, 1/2 degree C) and range.
      * Then tweak to be more precise when appropriate.
      */
 
     data->params = &device_params[data->kind];
 
     /* Save default sample time and resolution*/
     data->sample_time = data->params->default_sample_time;
     data->resolution = data->params->default_resolution;
 
     /* Enable the power */
     err = regulator_enable(data->vs);
     if (err) {
         dev_err(dev, "failed to enable regulator: %d\n", err);
         return err;
     }
 
     err = devm_add_action_or_reset(dev, lm75_disable_regulator, data);
     if (err)
         return err;
 
     /* Cache original configuration */
     status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
     if (status < 0) {
         dev_dbg(dev, "Can't read config? %d\n", status);
         return status;
     }
     data->orig_conf = status;
     data->current_conf = status;
 
     err = lm75_write_config(data, data->params->set_mask,
                 data->params->clr_mask);
     if (err)
         return err;
 
     err = devm_add_action_or_reset(dev, lm75_remove, data);
     if (err)
         return err;
 
     hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
                              data, &lm75_chip_info,
                              NULL);
     if (IS_ERR(hwmon_dev))
         return PTR_ERR(hwmon_dev);
 
     dev_info(dev, "%s: sensor '%s'\n", dev_name(hwmon_dev), client->name);
 
     return 0;
 }
 
 static const struct i2c_device_id lm75_ids[] = {
     { "adt75", adt75, },
     { "at30ts74", at30ts74, },
     { "ds1775", ds1775, },
     { "ds75", ds75, },
     { "ds7505", ds7505, },
     { "g751", g751, },
     { "lm75", lm75, },
     { "lm75a", lm75a, },
     { "lm75b", lm75b, },
     { "max6625", max6625, },
     { "max6626", max6626, },
     { "max31725", max31725, },
     { "max31726", max31725, },
     { "mcp980x", mcp980x, },
     { "pct2075", pct2075, },
     { "stds75", stds75, },
     { "stlm75", stlm75, },
     { "tcn75", tcn75, },
     { "tmp100", tmp100, },
     { "tmp101", tmp101, },
     { "tmp105", tmp105, },
     { "tmp112", tmp112, },
     { "tmp175", tmp175, },
     { "tmp275", tmp275, },
     { "tmp75", tmp75, },
     { "tmp75b", tmp75b, },
     { "tmp75c", tmp75c, },
     { "tmp1075", tmp1075, },
     { /* LIST END */ }
 };
 MODULE_DEVICE_TABLE(i2c, lm75_ids);
 
 static const struct of_device_id __maybe_unused lm75_of_match[] = {
     {
         .compatible = "adi,adt75",
         .data = (void *)adt75
     },
     {
         .compatible = "atmel,at30ts74",
         .data = (void *)at30ts74
     },
     {
         .compatible = "dallas,ds1775",
         .data = (void *)ds1775
     },
     {
         .compatible = "dallas,ds75",
         .data = (void *)ds75
     },
     {
         .compatible = "dallas,ds7505",
         .data = (void *)ds7505
     },
     {
         .compatible = "gmt,g751",
         .data = (void *)g751
     },
     {
         .compatible = "national,lm75",
         .data = (void *)lm75
     },
     {
         .compatible = "national,lm75a",
         .data = (void *)lm75a
     },
     {
         .compatible = "national,lm75b",
         .data = (void *)lm75b
     },
     {
         .compatible = "maxim,max6625",
         .data = (void *)max6625
     },
     {
         .compatible = "maxim,max6626",
         .data = (void *)max6626
     },
     {
         .compatible = "maxim,max31725",
         .data = (void *)max31725
     },
     {
         .compatible = "maxim,max31726",
         .data = (void *)max31725
     },
     {
         .compatible = "maxim,mcp980x",
         .data = (void *)mcp980x
     },
     {
         .compatible = "nxp,pct2075",
         .data = (void *)pct2075
     },
     {
         .compatible = "st,stds75",
         .data = (void *)stds75
     },
     {
         .compatible = "st,stlm75",
         .data = (void *)stlm75
     },
     {
         .compatible = "microchip,tcn75",
         .data = (void *)tcn75
     },
     {
         .compatible = "ti,tmp100",
         .data = (void *)tmp100
     },
     {
         .compatible = "ti,tmp101",
         .data = (void *)tmp101
     },
     {
         .compatible = "ti,tmp105",
         .data = (void *)tmp105
     },
     {
         .compatible = "ti,tmp112",
         .data = (void *)tmp112
     },
     {
         .compatible = "ti,tmp175",
         .data = (void *)tmp175
     },
     {
         .compatible = "ti,tmp275",
         .data = (void *)tmp275
     },
     {
         .compatible = "ti,tmp75",
         .data = (void *)tmp75
     },
     {
         .compatible = "ti,tmp75b",
         .data = (void *)tmp75b
     },
     {
         .compatible = "ti,tmp75c",
         .data = (void *)tmp75c
     },
     {
         .compatible = "ti,tmp1075",
         .data = (void *)tmp1075
     },
     { },
 };
 MODULE_DEVICE_TABLE(of, lm75_of_match);
 
 #define LM75A_ID 0xA1
 
 /* Return 0 if detection is successful, -ENODEV otherwise */
 static int lm75_detect(struct i2c_client *new_client,
                struct i2c_board_info *info)
 {
     struct i2c_adapter *adapter = new_client->adapter;
     int i;
     int conf, hyst, os;
     bool is_lm75a = 0;
 
     if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
                      I2C_FUNC_SMBUS_WORD_DATA))
         return -ENODEV;
 
     /*
      * Now, we do the remaining detection. There is no identification-
      * dedicated register so we have to rely on several tricks:
      * unused bits, registers cycling over 8-address boundaries,
      * addresses 0x04-0x07 returning the last read value.
      * The cycling+unused addresses combination is not tested,
      * since it would significantly slow the detection down and would
      * hardly add any value.
      *
      * The National Semiconductor LM75A is different than earlier
      * LM75s.  It has an ID byte of 0xaX (where X is the chip
      * revision, with 1 being the only revision in existence) in
      * register 7, and unused registers return 0xff rather than the
      * last read value.
      *
      * Note that this function only detects the original National
      * Semiconductor LM75 and the LM75A. Clones from other vendors
      * aren't detected, on purpose, because they are typically never
      * found on PC hardware. They are found on embedded designs where
      * they can be instantiated explicitly so detection is not needed.
      * The absence of identification registers on all these clones
      * would make their exhaustive detection very difficult and weak,
      * and odds are that the driver would bind to unsupported devices.
      */
 
     /* Unused bits */
     conf = i2c_smbus_read_byte_data(new_client, 1);
     if (conf & 0xe0)
         return -ENODEV;
 
     /* First check for LM75A */
     if (i2c_smbus_read_byte_data(new_client, 7) == LM75A_ID) {
         /*
          * LM75A returns 0xff on unused registers so
          * just to be sure we check for that too.
          */
         if (i2c_smbus_read_byte_data(new_client, 4) != 0xff
          || i2c_smbus_read_byte_data(new_client, 5) != 0xff
          || i2c_smbus_read_byte_data(new_client, 6) != 0xff)
             return -ENODEV;
         is_lm75a = 1;
         hyst = i2c_smbus_read_byte_data(new_client, 2);
         os = i2c_smbus_read_byte_data(new_client, 3);
     } else { /* Traditional style LM75 detection */
         /* Unused addresses */
         hyst = i2c_smbus_read_byte_data(new_client, 2);
         if (i2c_smbus_read_byte_data(new_client, 4) != hyst
          || i2c_smbus_read_byte_data(new_client, 5) != hyst
          || i2c_smbus_read_byte_data(new_client, 6) != hyst
          || i2c_smbus_read_byte_data(new_client, 7) != hyst)
             return -ENODEV;
         os = i2c_smbus_read_byte_data(new_client, 3);
         if (i2c_smbus_read_byte_data(new_client, 4) != os
          || i2c_smbus_read_byte_data(new_client, 5) != os
          || i2c_smbus_read_byte_data(new_client, 6) != os
          || i2c_smbus_read_byte_data(new_client, 7) != os)
             return -ENODEV;
     }
     /*
      * It is very unlikely that this is a LM75 if both
      * hysteresis and temperature limit registers are 0.
      */
     if (hyst == 0 && os == 0)
         return -ENODEV;
 
     /* Addresses cycling */
     for (i = 8; i <= 248; i += 40) {
         if (i2c_smbus_read_byte_data(new_client, i + 1) != conf
          || i2c_smbus_read_byte_data(new_client, i + 2) != hyst
          || i2c_smbus_read_byte_data(new_client, i + 3) != os)
             return -ENODEV;
         if (is_lm75a && i2c_smbus_read_byte_data(new_client, i + 7)
                 != LM75A_ID)
             return -ENODEV;
     }
 
     strscpy(info->type, is_lm75a ? "lm75a" : "lm75", I2C_NAME_SIZE);
 
     return 0;
 }
 
 #ifdef CONFIG_PM
 static int lm75_suspend(struct device *dev)
 {
     int status;
     struct i2c_client *client = to_i2c_client(dev);
 
     status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
     if (status < 0) {
         dev_dbg(&client->dev, "Can't read config? %d\n", status);
         return status;
     }
     status = status | LM75_SHUTDOWN;
     i2c_smbus_write_byte_data(client, LM75_REG_CONF, status);
     return 0;
 }
 
 static int lm75_resume(struct device *dev)
 {
     int status;
     struct i2c_client *client = to_i2c_client(dev);
 
     status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
     if (status < 0) {
         dev_dbg(&client->dev, "Can't read config? %d\n", status);
         return status;
     }
     status = status & ~LM75_SHUTDOWN;
     i2c_smbus_write_byte_data(client, LM75_REG_CONF, status);
     return 0;
 }
 
 static const struct dev_pm_ops lm75_dev_pm_ops = {
     .suspend	= lm75_suspend,
     .resume		= lm75_resume,
 };
 #define LM75_DEV_PM_OPS (&lm75_dev_pm_ops)
 #else
 #define LM75_DEV_PM_OPS NULL
 #endif /* CONFIG_PM */
 
 static struct i2c_driver lm75_driver = {
     .class		= I2C_CLASS_HWMON,
     .driver = {
         .name	= "lm75",
         .of_match_table = of_match_ptr(lm75_of_match),
         .pm	= LM75_DEV_PM_OPS,
     },
     .probe		= lm75_probe,
     .id_table	= lm75_ids,
     .detect		= lm75_detect,
     .address_list	= normal_i2c,
 };
 
 module_i2c_driver(lm75_driver);
 
 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>");
 MODULE_DESCRIPTION("LM75 driver");
 MODULE_LICENSE("GPL");
 